1). Field of the Invention
The present invention is concerned with automation of tests carried out using a cascade impactor.
2). Discussion of Related Art
Cascade impactors are in themselves well known. They are used to analyze particle size distribution in aerosols. A particularly important application is in the testing of inhalers—devices used to dispense a controlled pharmaceutical dose into the mouth and lungs of a patient. Inhalers are used to treat asthma and other conditions. The pharmaceutical drug is typically in powdered or liquid form, much of its bulk being made up of a carrier and only a small percentage by the active ingredient. In use the patient releases a controlled dose of the powder or liquid using a mechanical arrangement such as a trigger lever. The patient, then draws it into the lungs by sucking. Penetration of the drug—and hence of the active ingredient itself—into the lungs is affected by particle size, so during manufacture it is necessary to verify, by testing of sample inhalers, that a suitable particle size distribution is being achieved. The cascade impactor is used for this purpose.